Jan Woolf writes: Richard Hamilton (obituary, 14 September) was one of the key artists of the Free for All campaign against museum entry charges in the late 1990s. He designed the witty posters, entitled Free the South Kensington Three. One of these showed Raphael looking forlornly through imaginary bars at the Victoria and Albert Museum. He used images of Ada Lovelace for the Science Museum and Charles Darwin for the Natural History Museum.

Richard Hamilton's Free the South Kensington Three poster

It was a brilliant concept and the original artwork for each poster was taken into the permanent collection of the V&A on International Museum Day in May 1998. We had a fine demonstration on the steps of the V&A that day which Richard was due to attend, but he called that morning to say he wasn't feeling very well and would we mind banning him from the demo. "Of course not. You're banned," we said. "Thank you and good luck," he replied. "The posters will be with you by noon."

Richard was a committed activist and often put his pencil where his convictions were, but not at the expense of aesthetic integrity. A lifelong advocate of free museums, he drew fervently in the Science Museum as a boy. With charges in place, popping in daily would have been prohibitive for many artists.

An alliance of Bectu's national visual artists' branch, the National Campaign for the Arts, the National Arts Collection Fund, members of the House of Lords, MPs, individual artists and others, the Free for All campaign was a success, and any further attempt to charge for museum entry will be resisted as robustly and imaginatively. We still have Richard's posters.

Patrick O'Byrne writes:Richard Hamilton also designed the cover for the Beatles' White album, and the poster that came with it. I was working part-time in a record store in Dublin in December 1968 and well remember the sheer excitement and wonder when we unpacked the beautiful new albums, fresh from the wholesaler.